U.S. patent number 9,643,322 [Application Number 13/860,752] was granted by the patent office on 2017-05-09 for control method for a balancing lifting gear and balancing lifting gear.
This patent grant is currently assigned to Terex MHPS GmbH. The grantee listed for this patent is Demag Cranes & Components GmbH. Invention is credited to Holger Freitag, Giorgio Maccioni, Giuliano Persico.
United States Patent |
9,643,322 |
Freitag , et al. |
May 9, 2017 |
Control method for a balancing lifting gear and balancing lifting
gear
Abstract
A control method for a balancing lifting gear which includes a
lifting motor that can be actuated by a controller and uses a
control handle with a force sensor to lift and lower a
load-supporting device. In a "Balance" operating mode, the
load-supporting device, with or without a picked-up load, is raised
or lowered by the controller in response to a force applied by an
operator. In order to ensure disturbance-free handling of a load
when removing or attaching a load, a "Pick-up" operating mode or an
"Assemble" operating mode is selected, in which the load-supporting
device is moved independently without the influence of the force of
the operator by the controller in the lifting or lowering direction
in dependence upon the signals determined by the force sensor. A
balancing lifting gear which operates in accordance with the
aforementioned control method is also disclosed.
Inventors: |
Freitag; Holger (Bochum,
DE), Maccioni; Giorgio (Witten, DE),
Persico; Giuliano (Wetter, DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
Demag Cranes & Components GmbH |
Wetter |
N/A |
DE |
|
|
Assignee: |
Terex MHPS GmbH (Dusseldorf,
DE)
|
Family
ID: |
48095723 |
Appl.
No.: |
13/860,752 |
Filed: |
April 11, 2013 |
Prior Publication Data
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|
|
Document
Identifier |
Publication Date |
|
US 20130282178 A1 |
Oct 24, 2013 |
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Foreign Application Priority Data
|
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Apr 20, 2012 [DE] |
|
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10 2012 103 515 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B66D
3/18 (20130101); B25J 13/02 (20130101); B25J
13/085 (20130101); B66D 1/46 (20130101); B66D
1/56 (20130101); B66D 1/48 (20130101); B66D
1/40 (20130101) |
Current International
Class: |
B25J
13/08 (20060101); B25J 13/02 (20060101); B66D
3/18 (20060101); B66D 1/46 (20060101); B66D
1/56 (20060101); B66D 1/40 (20060101); B66D
1/48 (20060101) |
Field of
Search: |
;700/257
;254/266,273,275 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
20100584 |
|
May 2002 |
|
DE |
|
2177308 |
|
Apr 2010 |
|
EP |
|
9843911 |
|
Oct 1998 |
|
WO |
|
0069771 |
|
Nov 2000 |
|
WO |
|
Primary Examiner: Tran; Khoi
Assistant Examiner: Nguyen; Robert
Attorney, Agent or Firm: Gardner, Linn, Burkhart and Flory,
LLP
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:
1. A control method for a balancing lifting gear that lifts and
lowers a load-supporting device, said balancing lifting gear having
a lifting motor, a controller adapted to actuate said motor, a
control handle, said control handle including a force sensor that
produces a signal in response to a force applied by at least one
chosen from an operator, another object striking the
load-supporting device, another object placed on top of a load
supported by the load-supporting device, and the load supporting
device becoming hooked under another object, said method
comprising: providing said control handle an operating mode
selector that receives an operator selection from among at least a
Balance operating mode, a Pick-up operating mode, and an Assemble
operating mode; selecting from among the Balance operating mode,
the Pick-up operating mode, or the Assemble operating mode; when
the Balance operating mode is selected, raising or lowering the
load-supporting device in a vertical lifting or lowering direction
by the controller in response to the signal produced by the force
sensor in response to the force applied by the operator to the
control handle or the force applied to the load-handling device, or
the force applied to the load supported by the load-handling
device; when either the Pick-up operating mode or the Assembly
operating mode is selected, in response to the selection raising or
lowering the load-supporting device in a vertical lifting or
lowering direction by the controller by moving the load-supporting
device automatically to a desired position without a further force
applied to the control handle or to the load, while the controller
responds to the signal produced by a force applied to the force
sensor while automatically raising or lowering of the
load-supporting device in the vertical lifting or lowering
direction.
2. The control method as claimed in claim 1 including actuating the
lifting motor by the controller in the Pick-up operating mode such
that the load-supporting device is raised until the force sensor
measures a force which exceeds a preselected limit value, and the
controller subsequently changes to a Hold operating mode, in which
the load-supporting device is held in a stationary manner.
3. The control method as claimed in claim 2 wherein the preselected
limit value is preset in the controller in the Pick-up operating
mode.
4. The control method as claimed in claim 3 wherein the preset
limit value is in the range of 10 N to 100 N.
5. The control method as claimed in claim 1 further including a
Hold operating mode in which a brake which acts upon the
load-supporting device is actuated by the controller.
6. The control method as claimed in claim 1 wherein the Assembly
operating mode includes an Assemble I operating mode in which the
lifting motor is actuated by the controller in a manner that the
load-supporting device is automatically raised and lowered by the
controller in a taring procedure until a particular force in
relation to the load, the load supporting device and/or the control
handle is measured by the force sensor, wherein the particular
force is one that was previously tared.
7. The control method as claimed in claim 6 wherein the
load-supporting device is lowered when the measured force is larger
than the tared force and the load-supporting device is raised when
the measured force is smaller than the tared force.
8. The control method as claimed in claim 6 wherein the signal
produced by the force sensor in response to the force applied by
the operator to the control handle in the Assemble I operating mode
is monitored by the controller with an increased level of
sensitivity compared with in the Balance operating mode and the
signal produced by the force sensor in response to the force
applied by the operator is thus evaluated in the direction of a
lower speed for raising and lowering the load-supporting device in
the Assembly I operating mode than in the Balance operating
mode.
9. The control method as claimed in claim 6 wherein the speed for
raising and lowering the load-supporting device in the Assemble I
operating mode is selected by the controller from within a range of
2 mm/s to 8 mm/s.
10. The control method as claimed in claim 6 wherein the controller
determines an abutment, attachment, snagging or canting of the load
in the Assemble I operating mode by differential monitoring of the
force measured by the force sensor, in which specific temporal
differentials of the force measured by the force sensor are
compared to a limit value and the taring procedure is carried out
in the event that the limit value is exceeded.
11. The control method as claimed in claim 1 wherein said Assembly
operating mode includes an Assemble II operating mode in which the
lifting motor is actuated by the controller such that the
load-supporting device is raised as long as the signal produced by
the force sensor in response to the force applied by the operator
to the control handle does not act in a downwards direction, and
that the load-supporting device is lowered when the signal produced
by the force sensor in response to the force applied by the
operator to the control handle acts in a downwards direction.
12. The control method as claimed in claim 11 wherein the signal
produced by the force sensor in response to the force applied by
the operator to the control handle in the Assemble II operating
mode is monitored by the controller with an increased level of
sensitivity compared with a force applied in the Balance operating
mode and the signal produced by the force sensor in response to the
force applied by the operator to the control handle is thus
evaluated in the direction of a lower speed for raising and
lowering the load-supporting device in the Assemble II operating
mode than in the Balance operating mode.
13. The control method as claimed in claim 6 wherein a frequency of
direction changes of movement of the load-supporting device is
monitored by the controller in the Assemble I and Assemble II
operating modes and a speed at which the load-supporting device is
raised or lowered is reduced and/or a Hold operating mode is
selected if the frequency exceeds a particular limit value.
14. The control method as claimed in claim 1 wherein the speed for
raising and lowering the load-supporting device is selected by the
controller from the range of approximately 2 mm/s to approximately
10 mm/s in the Pick-up operating mode and in the Assemble II
operating mode.
15. The control method as claimed in claim 11 further including a
Weigh operating mode in which a load force acting upon the force
sensor is measured by the controller.
16. The control method as claimed in claim 15 wherein the Weigh
operating mode is started by the controller when the operator takes
the operator's hand off the control handle.
17. A balancing lifting gear, comprising: a lifting motor, a
controller that actuates said lifting motor, an operating mode
selector, and a control handle with a force sensor, said force
sensor produces a signal in response to a force applied by at least
one chosen from an operator, another object striking a
load-supporting device, another object placed on top of the load
supported by the load-supporting device, and the load-supporting
device becoming hooked under another object in an operation to lift
and lower a load-supporting device wherein said operating mode
selector receives an operator selection from among at least a
Balance operating mode, a Pick-up operating mode, and an Assemble
operating mode; wherein said controller is selectable to operate in
the Balance operating mode in which the load-supporting device,
with or without a picked-up load, is raised or lowered by the
controller in a vertical lifting or lowering direction in response
to the signal produced by the force sensor in response to the force
applied by the operator to the control handle or the force applied
to the load-handling device or the force applied to a load
supported by the load-handling device; and wherein said controller
is selectable to operate in the Pick-up operating mode or the
Assemble operating mode in which in response to the selection the
load-supporting device is raised or lowered by the controller in
the vertical lifting or lowering direction automatically to a
desired position without a further force applied to the control
handle or to the load, while the controller responds to the signal
produced from a force applied to the force sensor while
automatically raising or lowering of the load-supporting device in
the vertical lifting or lowering direction.
18. The control method as claimed in claim 1 wherein when either
the Pick-up operating mode or Assembly operating mode is selected
then the controller responds to the signal produced by a force
applied to the force sensor with increased sensitivity as compared
with the Balance operating mode or until a limit value is
reached.
19. The balancing lifting gear as claimed in claim 17 wherein said
controller responds to the signal produced from the force sensor
with increased sensitivity as compared with the Balance operating
mode or until a limit value is reached when the controller is
selected to operate in the Pick-up operating mode or the Assembly
operating mode.
Description
BACKGROUND OF THE INVENTION
The invention relates to a control method for a balancing lifting
gear and, in particular, for use with a lifting gear having a
lifting motor which can be actuated by a controller and uses a
control handle with a force sensor to lift and lower a
load-supporting device. The invention also relates to a balancing
lifting gear having a lifting motor which can be actuated by a
controller and uses a control handle with a force sensor to lift
and lower a load picking-up means, also referred to herein as a
load-supporting device.
The German utility model DE 201 00 584 U1 discloses a so-called
balancing lifting gear or a so-called cable balancer. A cable
balancer includes a cable winch, a control handle and a
load-supporting device and enables an operator to lift or lower a
load, which is fastened to the load-supporting device, in a type of
floating state in an almost weightless manner. A controller which
is allocated to the cable winch balances the weight force of the
load so that a manual force is applied by an operator to the load,
the load-supporting device, or the control handle effects lifting
or lowering of the load, depending upon the direction in which the
manual force is effective. The controller can select the lifting or
lowering speed in proportion to the applied force. In order to
determine the manual force, a force sensor is disposed in the
control handle at the transition from the upper end of the control
handle to the cable. The weight of the load can also be measured by
this force sensor and, by means of a change in weight force, it is
possible to determine the manual force which serves a control
variable for the controller and the lifting and lowering speed
determined therefrom. The response behavior of the cable balancer
can also be adjusted from gentle to aggressive in the
controller.
In addition to the previously described "Balance" operating mode, a
further operating mode of "Up/down control" is provided. For this
purpose, the control handle is provided with an actuating ring
which can be actuated in the upwards or downwards direction by the
operator using his thumb to apply a force. The actuating ring is
connected to a further force sensor, whose signals are supplied to
the controller for lifting and lowering the load. When the
actuating ring is used, a switch is made automatically from the
"Balance" operating mode to the "Up/down control" operating
mode.
It is generally known that such balancing lifting gears or cable
balancers are used in different industrial processes, in which
loads are moved and positioned in an exact manner by an operator.
This relates, e.g., to manufacturing processes, in which one
component is to be transported to another component and is to be
attached thereto. The balancing lifting gears have been developed
in order to reduce the amount of work for the operator in such a
case.
Laid-open document US 2005/0267638 A1 discloses a control system
for floor-free conveyors within the domain of assembly lines. The
control system can be configured to adapt the floor-free conveyors
in the form of cranes and balancing lifting gears, in particular
their movement paths, to suit the individual assembly tasks.
Semi-automatic movements can be provided or, e.g., the floor-free
conveyor can return automatically to a starting position. In
relation to the balancing lifting gears used, provision is made to
adapt their response behavior to suit the users. For this purpose,
maximum lifting and lowering speeds, maximum lifting and lowering
accelerations, maximum and minimum lifting heights and the response
sensitivity of the balancing lifting gear can be adjusted with
respect to the balancing lifting gear. For this purpose, a
corresponding display and various operating switches are provided
in the region of a handle of the balancing lifting gear. In this
control system, it is also possible to define specific regions, in
which the floor-free conveyors cannot enter, in order to prevent
collisions with parts of a building or machines, or the like.
SUMMARY OF THE INVENTION
The present invention achieves a simpler handling of a load with a
balancing lifting gear, in particular when raising, removing, or
attaching a load.
A control method, according to an aspect of the invention, for a
balancing lifting gear having a lifting motor, a controller adapted
to actuate the motor, a control handle with a force sensor is
adapted to lift and lower a load-supporting device in which, in a
"Balance" operating mode, the load-supporting device with or
without a supported load is raised or lowered by the controller in
response to a force applied by an operator, includes selecting from
a "Pick-up" operating mode or an "Assemble" operating mode. In the
"Pick-up" or "Assemble" operating modes, the load-supporting device
is moved with the controller independent of a force of an operator
in a lifting or lowering direction in response to signals
determined by the force sensor.
A control method 30, according to an embodiment of the invention,
is for controlling a balancing lifting gear having a lifting motor
which can be actuated by the controller and uses a control handle
with a force sensor to lift and lower a load-supporting device. In
a "Balance" operating mode 34, the load-supporting device, with or
without a picked-up load, is raised or lowered by the controller in
response to a force applied by an operator 42. When raising,
removing, or attaching a load from or to another component, a
"Pick-up" operating mode 36 or an "Assemble" operating mode 38, 40
is selected, in which the load-supporting device is moved
independently without the influence of the force of an operator by
the controller in the lifting or lowering direction in dependence
upon the signals determined by the force sensor 50. The at least
partially independent movement of the load-supporting device at
least in part eliminates the problem for the operator of adjusting
the movement speed of the load-supporting device. The operator can
thus concentrate on corrections to the movements in the horizontal
direction. None of his time is taken up with controlling the
vertical movement. Simpler handling of a load is achieved with a
balancing lifting gear.
The term "independent" is thus to be understood as a type of
automatic lifting and/or lowering movement, in which the operator
does not touch either the control handle or the load and/or the
load-supporting device and the controller of the balancing lifting
gear moves automatically to a desired position. The independent
movement allows speed and any contact forces which occur to be
controlled more effectively. Therefore, in the "Pick-up" operating
mode or in the "Assemble" operating mode, the movement of the
load-supporting device is at least partly taken out of the
operator's hands. "Independent" means, in this case, that this
movement takes place even when the operator does not apply any
force. The speed of the movement is not proportional to the
operator's force. The speed is predetermined and is typically
constant. However, it is possible to parameterize the force as well
as the speed during a calibration procedure. The "Assemble"
operating mode includes the two operating modes "Assemble I" and
"Assemble II".
The phrase "operator's force" relates primarily to forces which are
exerted by the operator, but also relates to forces which originate
from other objects which the balancer lifting gear cannot
distinguish from an operator's force. Forces originating from other
objects are produced such as when the load strikes against, is
placed on top of, or becomes hooked underneath other objects. The
"operator's force" thus corresponds to an external force acting
upon the force sensor.
In one mode of operation, the control method 30 provides that the
controller does not process the force which otherwise in the
"Balance" operating mode effects the independent movement in the
lifting or lowering direction. This mode of operation is
advantageously affected together with the "Assemble II" 40 and
"Pick-up" 36 operating modes. The operator can thus concentrate on
correcting the movements in the horizontal direction and/or the
control of the vertical movement is taken completely out of the
operator's hands.
In the "Pick-up" operating mode 36, the lifting motor is actuated
by the controller such that the load-supporting device is raised
until the force sensor measures a force which exceeds a preselected
limit value 44. Subsequently, a change is made by the controller to
a "Hold" operating mode in which the load-supporting device is held
in a stationary manner. After the limit value has been reached and
the load-supporting device is held in a stationary manner, an
operator can release a clamping device, or the like, in which the
load is held, and the load becomes free to be securely picked up. A
change can then be made back either to the "Balance" operating mode
or the "Up/down control" operating mode, or the "Hold" operating
mode can be maintained, in which no vertical movements of the load
are possible and in which a horizontal movement can be effected by
means of a swing arm or a movement of the balancing lifting gear
along a running rail. This "Pick-up" operating mode ensures,
particularly when a clamped workpiece is being picked up, that on
the one hand the holding force of the balancing lifting gear is
large enough to ensure secure pick-up of the workpiece, and on the
other hand is small enough to minimize the risk of canting or
slipping of the workpiece.
In the "Pick-up" operating mode 36, the limit value may be preset
in the controller. The limit value can have different values
depending upon the type of load or workpiece and optionally in
dependence upon the type of load-supporting device. In this case,
it is suitably selected to be as low as possible or just large
enough to ensure that the load is securely picked up. For example,
the limit value can be preset in the range of 10 N to 100 N.
In order to guide the load for specific handling tasks without the
load being raised or lowered by reason of the manual force applied,
a "Hold" operating mode is provided in which a brake which acts
upon the load-supporting device is actuated by the controller.
In one operating mode "Assemble I" 38, the lifting motor may be
actuated by the controller such that the load-supporting device is
independently raised and lowered by the controller in a taring
procedure until a force which is previously tared in relation to
the load, the load-supporting device and/or the control handle is
measured by the force sensor 46. Such an "Assemble I" operating
mode is used for attaching a load to another workpiece. This
otherwise presents the particular risk that the attachment of a
load to another workpiece will be interpreted incorrectly as an
operator's force acting in an upwards direction, which would lead
to an undesired raising of the load. Therefore, in this "Assemble
I" operating mode 38, forces which act from below and above and are
produced by manual forces of an operator or as previously described
in connection with load-handling are processed within the framework
of the taring procedure until the tared force is reached. The
operator can continue the assembly movement or move his hands away
from the load and the load-supporting device in order, after the
tared state has been reached, to continue the assembling procedure
on the basis thereof initially without any canting. In this mode of
operation, the load can be almost floating when it is attached to a
bar. This ensures that in the case of a larger force measured with
respect to the tared force, the load-supporting device is lowered
and in the case of a smaller force measured with respect to the
tared force, the load-supporting device is raised.
In the "Assemble I" operating mode 38, the force applied by the
operator may be monitored by the controller with an increased level
of sensitivity compared within the "Balance" operating mode and the
force applied by the operator is thus evaluated in the direction of
a lower speed for raising and lowering the load-supporting device.
This also applies to the disturbance forces during handling. This
increase in the level of sensitivity corresponds to a reduction in
the dynamics which in this regard is understood to mean that in
comparison with the "Balance" operating mode the dynamics are
reduced. On the basis of a typical maximum lifting and lowering
speed in the range of 10 m/min to 30 m/min in the "Balance"
operating mode in relation to a maximum evaluated manual force of
such as 30 N, the reduction in dynamics causes the maximum lifting
and lowering speed to change to a range of 5 m/min in the "Balance"
operating mode in relation to a maximum evaluated manual force of
30 N. The dynamics may be halved. In of the "Assemble I" and
"Balance" operating modes, the applied manual force may be
proportional to the lifting or lowering speed determined
therefrom.
In the "Assemble I" operating mode 38, the speed for raising and
lowering the load-supporting device may be adjusted or limited by
the controller to the range of 2 mm/s to 8 mm/s. By virtue of this
limited movement speed, the operator is afforded sufficient
reaction time to react to the movements of the load-supporting
device. These low speeds permit particularly exact monitoring of
the occurring force even when electronically or mechanically
induced delays occur as the force is being determined.
In the "Assemble I" operating mode 38, the controller may establish
any abutment, attachment, snagging or canting of the load caused by
disturbance forces by differential monitoring. In differential
monitoring, specific temporal differentials of the force measured
by the force sensor are compared to a limit value. In the event
that the limit value is exceeded within the "Assemble I" operating
mode, the taring procedure is started. Therefore, in the event of
the limit value being exceeded, this does not lead to a switch to
the "Hold" operating mode but rather to an automatic taring of the
load, which means that the operator can continue the handling work.
In comparison with the "Balance" operating mode, the limit value
established for the differential monitoring may amount only to
about 30% in the "Assemble I" operating mode. For example, in the
"Balance" operating mode, at a load force of 1000 N, the limit
value amounts to about 200 N/50 ms and, in the "Assemble I"
operating mode, it amounts to about 66 N/50 ms. The operator has
the opportunity to allow the controller to complete the taring
procedure or to influence it by specific manual forces, since the
modified balancing operation continues to be active within the
"Assemble I" operating mode.
In operating mode "Assemble II" 40, the lifting motor may be
actuated by the controller such that the load-supporting device is
raised as long as a force applied by an operator to the load, the
load-supporting device and/or the control handle does not act in a
downwards direction, and that the load-supporting device is lowered
when a force that is applied by an operator to the load, the
load-supporting device and/or the control handle, acts in a
downwards direction 48. Such an "Assemble II" operating mode is
used for attaching a load to another workpiece. This would
otherwise present the particular risk that the attachment of the
load to the other workpiece will be interpreted incorrectly as an
operator's force acting in an upwards direction, which would lead
to an undesired raising of the load. Therefore, in this "Assemble
II" operating mode 40, forces which act from below are ignored and
instead the load is moved constantly upwards with a type of
"uplift" as long as the operator does not apply a downwardly
directed force. The operator can thus complete the assembly task
more simply, as his intervention is reduced to the downwardly
acting manual force.
In the "Assemble II" operating mode 40, the force applied by the
operator may be monitored by the controller with an increased level
of sensitivity compared within the "Balance" operating mode and the
force applied by the operator is thus evaluated in the direction of
a lower speed for raising and lowering the load-supporting device.
Completion of the handling task by the operator can be facilitated
as a result, as in that case smaller measurement value changes of
the force sensor are already evaluated as a change in the
operator's force.
In the "Assemble I" and "Assemble II" operating modes, a frequency
of direction changes movement of the load-supporting device that
may be monitored by the controller. A speed at which the
load-supporting device is raised and/or lowered is reduced and/or a
change is made to the "Hold" operating mode when the frequency
exceeds a preselected limit value. In cases where the attachment of
the load to another object is complicated or in the end phase of
the attachment process, many movement corrections may be required
within a confined space. In this embodiment, the changes in the
movement direction can be registered in terms of time and the
number thereof within a certain time period, such as the last 20
seconds, can be used as a measure of the present frequency. If, in
this case, a limit value, such as 8 changes within 20 seconds, is
exceeded, this may be assessed as an indication that the assembly
process requires too frequent intervention by the operator. In
response to this assessment, the speed at which the load-supporting
device is lowered and/or raised may be reduced, whereby more time
is available to the operator to intervene and on the whole the
assembly procedure becomes smoother.
In the "Pick-up" operating mode and in the "Assemble II" operating
mode the speed for raising the load-supporting device may be
adjusted in the range of 2 mm/s to 10 mm/s in the controller. By
virtue of this limited movement speed, the operator is afforded
sufficient reaction time to react to the movements of the
load-supporting device. These low speeds permit particularly exact
monitoring of the occurring force even when electronically or
mechanically induced delays occur as the force is being
determined.
In a "Weigh" operating mode 41 a load, force which acts upon the
force sensor can be measured by the controller 49. From this load
force, the controller is able to determine the weight, since the
weight of the load-supporting device and of the corresponding part
of the control handle would have been determined in a preceding
step. Then, for the "Balance", "Assemble I" and "Assemble II"
operating modes the controller can use the signal of the force
sensor to determine a manual force or a disturbance force, since
the load force is now known in terms of a tare force which
continues to be applied to the force sensor.
The "Weigh" operating mode can be started by the controller when
the operator takes his hand away from the control handle. For this
purpose, a corresponding sensor for detecting a hand is disposed on
the control handle. In a first step, an optionally occurring
movement of the balancing lifting gear is then stopped, i.e., the
desired speed of the balancing lifting gear is set to zero.
A balancing lifting gear, according to another aspect of the
invention, includes a lifting motor, a controller that is adapted
to actuate the lifting motor, and a control handle with a force
sensor that is adapted to lift and lower a load-supporting device.
The controller is adapted to operate in a "Balance" operating mode
in which the load-supporting device, with or without a picked-up
load, is raised or lowered by the controller in response to a force
applied by an operator. The controller is adapted to operate in a
"Pick-up" operating mode or an "Assemble" operating mode in which
the load-supporting device is moved by the controller in the
lifting or lowering direction in dependence upon the signals
determined by the force sensor independent of a force applied by an
operator.
In accordance with another aspect of the invention, a simpler
handling of a load with a balancing lifting gear may be achieved,
in particular when raising, removing or attaching a load from or to
another component, by virtue of the fact that a lifting motor can
be actuated by a controller and uses a control handle with a force
sensor to lift and lower a load-supporting device operates with the
previously described control methods.
BRIEF DESCRIPTION OF THE DRAWINGS
An exemplified embodiment of the invention will be explained
hereinafter with reference to the Figures, in which:
FIG. 1 shows a block diagram of a balancing lifting gear in
accordance with an embodiment of the invention having a load
suspended therefrom;
FIG. 2 shows an electronic schematic diagram of the balancing
lifting gear used in FIG. 1;
FIG. 3a shows a block diagram of a workpiece in a clamping device
prior to being picked up by a balancing lifting gear;
FIG. 3b shows a block diagram of a workpiece, which is guided with
a balancing lifting gear, prior to being attached to another
workpiece; and
FIG. 4 shows a block diagram of a control method for a balancing
lifting gear.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings and the illustrative embodiments
depicted therein, FIG. 1 illustrates a balancing lifting gear 1 in
a greatly simplified manner. Disposed in a housing 2 in this case
are a lifting motor 3 and a housing controller 4a which is part of
a complete controller 4 for the balancing lifting gear 1. The
housing 2 is typically suspended in a positionally fixed manner
from a supporting construction, not shown, or from a travelling
mechanism which is movable along a rail, which are well known in
the art. The lifting motor 3 uses a transmission 10 to drive a drum
11 (see FIG. 2) onto which or from which a cable 5 can be wound up
and unwound, respectively. Cable 5 serves as a flexible support
means for lifting and lowering a load 20. It is also feasible to
use textile bands or chains. The lifting motor 3 is preferably
formed as an electric lifting motor; however, it can also be a
pneumatic motor or hydraulic motor. A partial length of the cable 5
is unwound and hangs downwards out of the housing 2. A control
handle 6 having various operating elements 6a is disposed at a
lower, load-side end of the cable 5. The control handle 6 in the
illustrated embodiment is T-shaped in formation and has a
cylindrical gripping region for handling the load 20 and an
operating region, which widens upwards in a T-shaped manner, for
accommodating the operating elements 6a which the operator can
easily reach using his thumb. The operator can use the operating
elements 6a to select between different operating modes of the
balancing lifting gear 1 and also to control the balancing lifting
gear 1 manually in an "Up and down control" operating mode.
Also, disposed in the operating region is a display 6b which
displays the respective operating mode, status reports and any
malfunction statuses. The control handle 6 also has a handle
controller 4b which is a further part of the complete controller 4
for the balancing lifting gear 1. The handle controller 4b is
connected to the controller 4 via an optionally wireless
connection, not illustrated. Fastened to the lower end of the
control handle 6 is a load picking-up means, such as a
load-supporting device 9, to which a load 20 is attached. In the
present case, the load-supporting device 9 is formed as a hook but
can also be a lug or a gripper. The connection of the
load-supporting device 9 to the control handle 6 is formed as a
coupling, in order to permit an easy change of the load-supporting
device 9.
Located in the interior of the control handle 6 is not only the
handle controller 4b but also a force sensor 7 which measures a
force acting between the cable 5 and the load-supporting device
9.
An operator whose hand 15 is schematically illustrated can guide
the load 20 in a lifting and lowering direction by means of the
control handle 6 in a first operating mode designated as "Up/down
control". For this purpose, the operator can use the operating
elements 6a disposed in the control handle 6. Alternatively, the
control handle 6 can have a further force sensor, not illustrated,
and disposed therein which supports the control handle 6 on the
cable 5 or load-supporting device 9. This force sensor can then be
used to determine upwardly or downwardly directed control forces of
the operator on the control handle 6 which are then converted by
the controller 4 into commands for lifting or lowering the
load-supporting device 9. As soon as the operator takes hold of the
control handle 6, a switch is made to the "Up/down control"
operating mode. For this purpose, a corresponding sensor can be
provided on the control handle 6 which detects the presence of the
operator's hand.
In a further operating mode designated as "Balance", the operator
can effect lifting and lowering of the load 20 by directly acting
upon the load 20 or the load-supporting device 9 can effect lifting
or lowering of the load 20. In this case, forces exerted upon the
load 20 by the operator are translated into control commands for
the lifting motor 3, so that the load 20 is moved in the direction
corresponding to the direction in which the operator applies force.
In this case, the operator senses the lifting or lowering of the
load 20 as being quasi weightless. In the "Balance" operating mode,
the handle controller 4b determines the operator's force by
subtracting the weight force of the load-supporting device 9, the
load 20 and the control handle 6 from the force registered by the
force sensor 7. From this, control parameters for the lifting motor
3 are determined. As long as the load 20 is moved freely up and
down, the Balance mode represents an ideal mode of operation. In
the event of abutment, attachment, snagging or canting of the load
20, the balancing lifting gear 1 is protected by means of the
controller 4 via so-called differential monitoring.
Within the framework of the differential monitoring, the controller
4 monitors the change in the measured force over time. If this
differential exceeds a previously established limit value stored in
the controller 4, the controller 4 changes automatically from the
"Balance" operating mode to the "Hold" operating mode. For example,
in the "Balance" operating mode, at a load force of 1000 N, the
limit value amounts to about 200 N/50 ms. The time of 50 ms
corresponds to a control cycle. Starting from the now reached
"Hold" operating mode, the operator now has the opportunity to
select between the "Pick-up", "Assemble I" and "Assemble II"
operating modes for the handling task due to be carried out.
A brake 8 which is disposed in the housing 2 is used in the
operating mode designated as "Hold". The load 20 is held at the
height it has been taken up to and the operator can guide the load
20, which is suspended from the balancing lifting gear, directly or
by taking hold of the load-supporting device 9, without the forces
exerted upon the load 20 causing the load 20 to be raised or
lowered. In this case, the free length of the cable 5 is thus kept
constant even when the operator exerts forces along the cable 5.
This operating mode can be used when the balancing lifting gear 1
is suspended from a travelling mechanism which is manually movable
along a rail. The operator can thus pull the load 20 along the
rail. A swivel arm can also be provided instead of the rail.
There is also a "Weigh" operating mode for providing the controller
4 in the other operating modes of "Balance", "Assemble I" and
"Assemble II" with the opportunity of using the signal of the force
sensor 7 to determine a manual force or a disturbance force. In the
"Weigh" operating mode, the controller 4 uses the signal of the
force sensor 7 to determine a load force in terms of a tare force.
For this purpose, it is necessary for the load 20 to be suspended
freely from the cable 5 and not to be influenced by an operator's
hand 15 or by other disturbance forces. Therefore, it is possible
for the controller 4 to start the "Weigh" operating mode
automatically when the operator takes his hand 15 off the control
handle 6. For this purpose, a corresponding sensor (not shown) for
detecting the hand 15 on the control handle 6 is disposed on the
control handle 6. Beforehand, a still optionally occurring movement
of the balancing lifting gear 1 is stopped, i.e., the desired speed
of the balancing lifting gear is set to zero. The controller 4 can
then use the measured load force to determine the weight of the
load 20, since the weight of the currently used load-supporting
device 9 and of the corresponding part of the control handle 6 have
been determined in a preceding step using the "Weigh" operating
mode. The load force or tare force relevant for the controller 4
includes the weight forces of the currently used load-supporting
device 9 and of the corresponding part of the control handle 6.
FIG. 2 illustrates a schematic diagram of the balancing lifting
gear 1 shown in FIG. 1. In addition to FIG. 1, it is illustrated
that the lifting motor 3 with the brake 8 drives a cable drum 11
via a transmission 10. The cable 5 for lifting and lowering the
load 20 is wound up and unwound using the cable drum 11. Disposed
between the cable drum 11 and the load 20 is the force sensor 7
which measures the force FS in the cable 5. In the event that only
one load 20 is suspended from the cable 5 and no operator's force
FB acts upon the load 20, the control handle 6 or the
load-supporting device 9, the cable force FS measured by the force
sensor 7 corresponds to the load force FL of the load 20 suspended
from the cable 5. The load force FL is typically derived from the
mass m of the load 20 multiplied by the gravity acceleration g. The
load force FL can be known or can be supplied manually to the
controller 4 or can be determined in a "Weigh" operating mode in
the case of a load 20 which is freely suspended from the cable 5.
In the event that in addition to the load 20, an operator's force
FB also acts upon the cable 5, the cable force FS measured by the
force sensor 7 corresponds to the sum of the load force FL and
operator's force FB and any disturbance forces FE. A force value
FB1 which corresponds virtually to the operator's force FB but also
contains any disturbance forces FE is determined from the
difference of the cable force FS and the load force FL in a
summation member 12. In a filter 13, a desired rotational speed
nsoll is determined, as a control variable for a rotational speed
controller 14 from the calculated force value FB1. The filter 13 is
formed as a 2.sup.nd order low-pass filter, whose buckling
frequency is adjusted with the aid of the tare force determined in
the "Weigh" operating mode. The rotational speed controller 14
formed as a PI-controller is provided to a frequency converter 16
to actuate the lifting motor 3, by means of which the lifting or
lowering of the load 20 desired by the applied operator's force FB
is then performed. The rotational speed controller 14 operates in a
closed loop system, which means that the lifting motor 3 is
allocated a rotational speed sensor 17, whose rotational speed
measurement signal nist is supplied as an actual variable to the
rotational speed controller 14.
FIGS. 3a and 3b illustrate operating situations, in which neither
the "Balance" operating mode nor the "Hold" operating mode is
ideal. FIG. 3a illustrates a load 20 in the form of a workpiece
which is clamped in a clamping device 21, such as in a turning
lathe. The workpiece 20 is to be removed from the clamping device
21 with the aid of the balancing lifting gear 1. For this purpose,
the workpiece 20 has a loop-shaped lifting means 22, which is
suspended from the load-supporting device 9, clasped around it in
the region of its centre of gravity. Then, in the "Balance"
operating mode, the lifting means 22 is conventionally clamped in a
manner induced by a manual force. In this case, the workpiece 20
continues to be held in the clamping device 21. Bracing of the
lifting means 22 presents the risk that the lifting means 22 will
be clamped either excessively or insufficiently. In the event that
the lifting means 22 is clamped excessively, releasing the clamping
device 21 can cause the workpiece 20 to be raised further and
become canted in the clamping device 21. Alternatively, in the
event that the lifting means 22 is insufficiently clamped,
releasing the clamping device 21 can cause the workpiece to slip
out of the clamping device 21 and then be brazed in a jerky fashion
by the lifting means 22.
For this operating procedure of picking up a workpiece 20 from a
clamping device 21, a "Pick-up" operating mode can be selected on
the control handle 6. After activation of this operating mode, the
operator lets go of the control handle 6 and also the
load-supporting device 9 and the load 20, and the load-supporting
device 9 is independently raised at a speed of, e.g., 2 mm/s until
the force registered by the force sensor 7 has reached a limit
value parameterized in the controller. Typical limit values are
approximately 10 to 100 N. The selectable speeds are in the range
of 2 mm/s to 10 mm/s. This serves as an indication of secure but
not excessively tight clamping of the lifting means 22 and thus
holding of the workpiece. The load-supporting device 9 is then
independently stopped and the balancing lifting gear 1 changes to
the "Hold" operating mode. The operator can then release the
clamping device 21 and guide the workpiece 20 out laterally.
In general, the "Pick-up" operating mode can be used for handling
tasks, in which workpieces or loads 20 are transferred from a held
or clamped appendage to the balancing lifting gear 1 without, in
this case, being lowered initially onto a floor or other
object.
Further operating modes "Assemble I" and "Assemble II" are
explained hereinafter with reference to FIG. 3b. FIG. 3b
illustrates a load-supporting device 9 which is formed as a gripper
and by means of which a load 20 in the form of a hollow cylinder,
wheel or pipe is raised. The load 20 is illustrated as picked up in
the region of its centre of gravity and is, therefore,
substantially horizontally aligned with its longitudinal extension.
In the present case, the handling task is illustrated as consisting
of attaching the load 20 to a stationary bar 23 supported on a wall
or another component. The bar 23 is to be understood as being
symbolic and is to serve as a type of placeholder for all manner of
components, in which comparable assembly tasks are to be completed.
The bar 23 can thus be, for example, a spindle, a mandrel or a
chuck of a turning lathe. Since the inner diameter of the hollow
cylinder and the outer diameter of the bar 23 differ only slightly,
this handling task presents a great risk that the hollow cylinder
and the bar 23 will cant with one another, since in the "Balance"
operating mode, attachment of the load 20 to the bar 23 or a
snagging of the load 20 on the bar 23 are evaluated by the
controller 4 as force signals for lifting and lowering.
For such handling tasks, the "Assemble I" operating mode or
alternatively "Assemble II" operating mode can be selected on the
control handle. When selecting the "Assemble I" operating mode, the
sensitivity in the controller 4 is increased and at the same time
the load changes (differentials in the load measurement) are
recorded more sensitively. In this regard, increasing the
sensitivity is understood to mean that in comparison with the
"Balance" operating mode the dynamics are reduced. On the basis of
a typical maximum lifting and lowering speed in the range of 10
m/min to 30 m/min in the "Balance" operating mode in relation to a
maximum evaluated manual force of, for example 30 N, the reduction
in dynamics changes the maximum lifting and lowering speed to a
range of 5 m/min in the "Balance" operating mode in relation to a
maximum evaluated manual force of 30 N. In the illustrated
embodiment, the dynamics are halved. In this case, i.e., in the
"Assemble I" and "Balance" operating modes, the applied manual
force typically continues to be proportional to the lifting or
lowering speed determined therefrom. Moreover, at the beginning of
the "Assemble I" operating mode, the total of the load 20,
load-supporting device 9 and control handle 6 are weighed by the
"Weigh" operating mode and the balancing lifting gear 1 is tared if
this has not already taken place beforehand. The controller 4 thus
knows the load force FL and can thus determine the operator's force
FB and any disturbance forces. If the load 20 then abuts against
the bar 23 during horizontal assembly, the controller 4 then begins
to tare the balancing lifting gear 1 by means of independent slow
lifting or lowering movements. Any abutment, attachment, snagging
or canting of the load 20 is established by the controller via
so-called differential monitoring. In comparison with the "Balance"
operating mode, the limit value established for the differential
monitoring amounts only to about 30% in the case of the "Assemble
I" operating mode. For example, in the "Balance" operating mode, at
a load force of 1000 N the limit value amounts to about 200 N/50
ms, and in the "Assemble I" operating mode it amounts to about 66
N/50 ms. The time of 50 ms corresponds to a control cycle. In the
"Assemble I" operating mode, the assembling speeds are in the range
of 2 mm/s to 8 mm/s. If the limit value is exceeded, the taring
procedure begins automatically in the "Assemble I" operating mode.
The operator then has the opportunity to allow the controller 4 to
complete the taring procedure or to influence it by specific manual
forces, since the modified balancing operation continues to be
active within the "Assemble I" operating mode.
Whether the controller 4 causes a movement of the load in the
lifting or lowering direction in conjunction with the commenced
taring procedure depends upon whether the force sensor 7, starting
from its tared state, measures a larger or smaller force in
comparison with the previously tared load force. A larger measured
force signifies a strike against the mandrel 23 from below and,
therefore, the load 20 is lowered. A smaller measured force
otherwise results in the load being raised. The operator can
continue the assembly procedure by pushing in a horizontal
direction until the load 20 abuts against another object. By means
of this method, a load can be almost floating when it is fitted
onto a mandrel or into a chuck. When the load 20 has reached its
end position, the operator opens or releases the load-supporting
device 9 and switches to the "Balance" or "Up/down control"
operating mode.
In the "Assemble II" operating mode, upwardly directed forces onto
the load-supporting device 9, the load 20 and the control handle 6
are ignored and do not cause the load 20 to be raised. However, in
this operating mode it is provided that the load-supporting device
9 is raised at a low speed of 5 mm/s, for example, it is subjected
to a type of artificial "uplift". Furthermore, the level of
sensitivity with which the force measured by the force sensor 7 is
registered is increased. If a downwardly directed operator's force
is registered, the load-supporting device 9 is lowered at a
constant speed of 5 mm/s. The selectable speeds are in the range of
2 mm/s to 10 mm/s. Furthermore, a verification is made as to how
often changes in the movement direction of the load-supporting
device 9 occur. If, e.g., more than 20 changes occur within 20
seconds, this serves as an indication that the operator is required
to intervene too frequently. In this case, the speeds for lifting
and for lowering are reduced, in order to afford the operator more
reaction time or to change to the "Hold" operating mode.
Therefore, in the "Assemble II" operating mode, the operator can
effect the slight lowering of the load 20 solely by means of a
downwardly directed force in cooperation with the automatic uplift,
in order to be able to slide the load onto the bar 23, and at the
same time the advantage of the balancing lifting gear 1, namely,
that the load 20 appears almost weightless, is retained.
While the foregoing description describes several embodiments of
the present invention, it will be understood by those skilled in
the art that variations and modifications to these embodiments may
be made without departing from the spirit and scope of the
invention, as defined in the claims below. The present invention
encompasses all combinations of various embodiments or aspects of
the invention described herein. It is understood that any and all
embodiments of the present invention may be taken in conjunction
with any other embodiment to describe additional embodiments of the
present invention. Furthermore, any elements of an embodiment may
be combined with any and all other elements of any of the
embodiments to describe additional embodiments.
* * * * *